1. Field of the Invention
The present invention relates to a substation of the type defined in the preamble to claim 1, and to a method of the type described in the preamble to claim 18.
2. Discussion of the Background
Conventional switchgear stations for high voltage are generally placed outdoors and take a considerable amount of space. The switchgear station is assembled on site and the components connected together. In view of its size and, in the eyes of many people, its unsightly appearance, these have generally had to be located far from residential districts and other areas frequented by people. They are therefore often located far from built-up areas. In many cases this results in undesired restriction of their localisation. Besides which, the construction of a switchgear station on site is relatively costly.
Since many towns have expanded over the years and existing substations which, at the time they were built, were situated outside the built-up area, are often now in the middle of the urban area. Environmental and space problems are thus encountered when such a station has served its time and is to be re-built.
In the present patent application the concept of high voltage relates to a voltage level of 52 kV and upwards, preferably up to 145 kV.
In an attempt to achieve more compact substations it is already known to enclose the substation components in hermetically sealed gas containers, with the components surrounded by SF.sub.6 -gas. The gas causes increased resistance to flashover, thus enabling t h e requirements for a safe distance between components at different voltage levels to be reduced so that a more compact manner of construction is possible. However, enclosing the components in such gas containers is extremely expensive. The gas enclosures must also be monitored for leakage risks, which further increases operating costs.
Substations with gas-insulated switchgear stations are therefore complicated, take a long time to repair after a fault, and complicate any extension with additional compartments, particularly after a long time when it may be difficult to obtain spare parts. The service life of a substation is approximately 30 years.
To avoid the drawbacks associated with substations in the open air and with substations surrounded by gas, it is also already known to enclose parts of the substation in a building in an environment of air. Examples of this can be found in SU 1,798,845, SU 801,166, FR 2,579,031, GB 916,391 and DE 4,139,177.
Both the SU publications show how the components in a switchgear station are enclosed in a building cell. This design results in extremely high buildings, approximately 20 meter, and the station must be supplied with overhead lines. Nothing is indicated as to how the other components in a substation including the building cell are arranged.
FR 2,579,031 shows a substation in which the high-voltage switchgear station is arranged in an air-insulated building constituting several floors. The supply lines are overhead lines. The transformers are situated outside the building.
GB 916,391 shows how a substation for lower voltages is housed in a building with aluminium walls.
DE 4,139,177 shows how the high-voltage switchgear station in a substation is arranged in a building constituting several floors. The switchgear station is supplied by overhead lines. How other parts of the substation are designed is not revealed.
The known examples in which parts of an air-insulated substation are enclosed in a building enable the drawbacks associated with substations in the open air or substations surrounded by gas to be avoided to a certain extent. However, none of the arrangements described above fully offers the opportunity to arrange an air-insulated substation at high voltage which is compact, service-friendly and which causes minimal disturbance so that it can be situated in an urban environment without problem.